Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$101.45	10.346%	$111.946	$111.95	$111.95	$111.90
Purchase #2	$168.84	9.731%	$185.2698	$185.27	$185.25	$185.30
Purchase #3	$43.54	9.366%	$47.618	$47.62	$47.60	$47.60
Purchase #4	$76.50	10.495%	$84.5287	$84.53	$84.55	$84.50
Purchase #5	$136.62	3.443%	$141.3238	$141.32	$141.30	$141.30
Purchase #6	$95.51	5.136%	$100.4154	$100.42	$100.40	$100.40
Purchase #7	$106.56	8.407%	$115.5185	$115.52	$115.50	$115.50
7 purchase totals =	$729.02		$786.6202	$786.63	$786.55	$786.50